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451.
452.
马文坡 《运载火箭与返回技术》2007,28(4):23-27
介绍了卫星光学遥图像获取与图像处理一体化优化设计的思路;运用通用像质方程(GIQE)对于利用小相对孔径光学系统和调制传递函数补偿(MTFC)方法得到的图像的品质与利用相对较大相对孔径光学系统得到的图像的品质进行了对比分析。 相似文献
453.
Werner Däppen 《Space Science Reviews》1998,85(1-2):49-60
The equation of state is one of the three fundamental ingredients used to construct stellar models. The plasma of the interiors
of stars such as the Sun is only slightly non-ideal. However, the extraordinary accuracy of the helioseismological data requires
refined equations of state. It turned out to be necessary to include a Coulomb correction, commonly evaluated in the Debye-Hückel
approximation. Higher-order non-ideal effects have implications as well, both for plasma physics and for solar physics. As
a typical example, the recently studied thermodynamic consequence of excited states in compound particles is discussed. This
effect is of considerable relevance in the helioseismic determination of the helium abundance in the solar convection zone.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
454.
Douglas Gough 《Space Science Reviews》1998,85(1-2):141-158
Standard solar models, although they are free from the influence of much of the fluid motion that is bound to be present in
the Sun, have been shown by helioseismology to represent the spherically averaged structure of the Sun amazingly well. This
state of affairs has come about after painstaking refinements by a great many people of the pertinent microphysics, including
that which controls the equation of state, the opacity, the nuclear reaction rates and the diffusion that inhibits gravitational
segregation of chemical elements. It has instilled confidence in the modellers in being able to predict the composition of
the solar interior. But there are consequences of the flow, related particularly to redistribution of chemical species, that
can be difficult to identify observationally, yet which may degrade any inferences we might make. Their potential presence
must at least be acknowledged by anyone who tries to asses the reliability of the models. This report summarizes the discussions
in the preceding pages of this volume of the current theoretical and observational status of the subject, pointing to many
of the caveats that have been raised, and attempting at the same time to put them into a seemingly coherent discourse in the
context of our present understanding of the workings of the solar interior.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
455.
针对二维欧拉方程研究了一类高分辨正性保持波尔兹曼型差分格式,首先分析了波尔兹曼方程和欧拉方程之间的关系;然后,利用一种特殊的插值技术构造了一类高分辨波尔兹曼型差分格式.最后通过数值实验验证了格式的实用性和有效性. 相似文献
456.
457.
The Hopkinson pressure bar tests for base metal and friction stir jointing(FSJ) jointed region of 7022 a- luminum alloy are carried out at different temperatures and strain rates. The temperature is 30--400 ℃ and the strain rate is 1 200-5 000 s 1. High strain rate for base metal and FSJ jointed region of 7022 aluminum alloy are studied. The corresponding stress-strain curves are obtained. The results show that the flow stresses of base metal and FSJ jointed region of 7022 aluminum alloy decline with the increase of temperature and increase with the in- crease of strain rate. Furthermore, the constitutive equation for base metal and FSJ jointed region of 7022 alumi- num alloy at high temperature and high strain rate is obtained based on Johnson-Cook model. 相似文献
458.
459.
介绍了应用Levenberg-Marquardt迭代法计算局部应力和局部应变的工作.Levenberg-Marquardt迭代法是求解超越方程的一种常用数学方法,但是缺点是程序比较复杂,计算效率较低,因此本文目的是找到一种程序实现简单、计算效率高、计算精度满足要求的计算方法,选择了二分法,并且对比分析了二分法和Leve... 相似文献
460.
网格自适应是一种有效减少解与网格相关性,改善计算结果的重要途径。给出了一种基于误差估计的伴随网格自适应计算技术,定义了基于误差估计的自适应准则,给出了非结构四面体网格单元细化剖分规则,以及一般的网格自适应流程,介绍了一种基于Rechardson外推的网格收敛技术,运用本文提供的方法对NLR7301翼型进行了数值计算研究,数值试验表明给出的网格自适应具有较高的可有效改善计算结果。 相似文献